Automatic air conditioning system



Jan. l0, 1939. L. B. MILLER Er AL 2,143,356 AUTOMATIC AIR CONDITIONING SYSTEM4 Filed sept. 10, 1934 2 'sheets-sheet 1 Fhgnj Zoo I7 EVAPo nAToR STEAM BQILER ovm-lens."

/N V'EN TORS Leo. 5. Mllerv JYeDJ'y f7.7 Bevan BY Tiff/,Q v/W'TORNEY MVM L. Bj MILLER ET AL Jan. 10, 1939.

AUTOMATIC AIR CONDITIONING SYSTEM- 2 sheets-s`neet 2 Filed Sept. 10,. 1934 NNN l @SW3 ova :YN EN www NNN QM'N N ,/NVEN TOJ O. Miller Le Helm @Y f/,e ATTORNEY 45 perature responsive thermostat.v

Patented Jan. 1o, 1939 UNITED STATES PATENT OFFICE AUTOMATIC AIR CO NDITIONING SYSTEM Leo B. Miller and Henry F. Dever, Minneapolis,

Minn., assignors to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware f Application September 10, `1934:, Serial No. 743.408

l5 Claims.

at one outdoor temperature to a: minimum flow upon a predetermined change in outdoor .temperature, the minimum iiow thereafter y being maintained irrespective of further outdoor temperature changes in the same direction, the flow of outdoor air to the space being additionally conf trolled by a space temperature responsive thermostat arranged to reduce the outdoor air iiow to the space when the space temperature reaches f an undesired value by reason of changes in the outdoor temperature. The arrangement is preferably such that the space temperature respon-V` sive thermostat operates to prevent the flow of outdoor air to `the space when the outdoor temperature is such as to require a minimum flow of outdoor airy to the space and the space temperature, as a result of such abnormal outdoor temperaturefalso becomes abnormal. J 'I'his phase o! the invention is particularlyuseiul inconnection withsummer cooling wherein it is desirable to provide thespace to be controlled with some i'resh outdorair at al1 times. the space thermostat completely preventing the takingv in of any outdoor air only when vthe outdoor'v temperature becomes so excessive as to raise the indoor temperature unduly. v

' A further object ot the invention is the-provision of an outdoor air flow control mechanism of 40 the class above described in combination with temperature changing means arranged to'change the temperature of the space in an effort to maintain the same constant or within desired limits and' preferably under the control of aspace tem- A iugjher object ofthe invention is the provision oi' means for automatically and selective] heating or cooling a space dependent upon the demands. The demands are preferably measured 50 by changes in'loutdoor temperature,aand, in order tfo avoid hunting, the arrangement preferred is one wherein there is an appreciable differential between the outdoor' temperature at which .the system is placed onda heating cycle or a cooling u cycle,-

Another object of thev invention is the provision Vof an improved heating and cooling system in which both heating and cooling is accomplished by the use of steam, the Jsteam preferably being furnished by a single boiler.

Another object of the invention is the provision of an improved control system for a steam jet or ejector type cooling unit, and particularly one of the types employinga plurality of stages or electors. v

Other objects of the invention include the prothe temperature and relative humidity of a space is controlled regardless of the outdoor temperature conditions and also include the various mechanisms set forth above both singly and in combination.

Other objects of the rinvention will be found in the detailed description, the appended claims, and the drawings.

For a more complete understandingfof the invention, reference may be had to the following description and the accompanying drawings, in which:

Fig. l is a diagrammatic showing of the complete system;

Fig` 2 is a diagrammatic showing of the control mechanism i'or the mixing dampers and the face andby-pass dempers and part of the control of the heating coil valve; and

vision of "an improved control system by which Y Fig. 3 is a schematic showing of the details of one of the control devices utilized in controlling the mixing dampers.

Referring rst to Figi ofthe drawings, the system of the present'invention includes an air conditioner herein shown as comprising an air ,conditioning chamber I0 that discharges into the 'which is driven by an electric motor I6 through suitable means such as a belt I1, causes air to be circulated through dthe lair conditioning chamber "Pand discharged into the room or space to be conditioned. 'The air conditioning chamber I0 -is provided with a partition IB which divides the entrance portion of the air conditioning chamberY I0 into a heating chamber I8 and a by-pass chamber 20. A heating coil 2| is located in the trolled by an electricslv operated valve 3|.

heating chamber I9. The proportionate flow of air through the heating chamber |9 and by-pass chamber is controlled by face dampers 22 and by-pass dampers 23 which are likewise controlled in a manner that will be described in detail hereinafter. The air conditioning chamber l0 is also provided with a cooling coil 24, a water spray 25, and a dehumidifying coil 26.

Water from any desired source; such as cityor tap water, is supplied to the spray 25 by means of a pipe 30, the flow of water through which is con- This valve 3| is contri" snong other things, by a relative humidity responsive device generally indicated at 32. This relative humidity responsive ldevice 32 includes an arm 33 which is pivoted at 34 and carries a mercury switch of ordinary construction indicated at 35. The arm 34 is actuated by a humidity responsive element 36 that is herein shown as comprising a plurality of strands of hair having one of their ends secured as at 31, whereas their other ends are attached to the lever 33 as .indicated at 38. A coiled tension spring 39 operates to place the hair element 36 under the proper stress. 'The' arrangement is such that if the relative humidity decreases to some predetermined value, say thirty-ve to forty per cent, th'e hair element 36 will shrink suiilciently to move arm 33, and therefore mercury switch 35, to positions opposite that shown` in Fig. 1 lwherein the circuit through mercury switch will be closed.

Cold or chilled water is supplied to the cooling and dehumidifying coils 24 and 26 by means of a steam jet ejector generally indicated at 45. This steam jet ejector includes a primary ejector 46 which communicates with a primary condenser 41, and likewise includes secondary ejectors 48 and 49 which communicate with an inter and after condenser 50. An evaporator 5| which contains the water to be chilled communicates with the primary ejector 46 by pipe means shown at 52; 'I'he evaporator 5| is also connected toa circulator 53, that includes an electric motor 54, by means of a pipe' 55. The circulator ,53 is in turn connected to the cooling coil 24 through an electrically operated valve 56 by means of pipes 51 and 68 and is connected to the dehumidifying coil 26 through an electrically operated valve 59 by whichis pivoted at 11'.V The actuating element of* means of pipes 51 and 60.

The cooling coil valve 56 is controlled by a temperature controller generally indicated at 65.

which includes a bellows 66 that communicates with :kcontrol bulb 61 by means of a tube 68, it being understood that the bellows, tube, and bulb are charged with a proper amount of suitable volatile uid, as is well-known in the art. The bellows 66 operates a lever 69 thatl is pivoted at 10 and carries a double circuit mercury switch 1 I. This temperature controller 65 responds to the temperature of the room or space to be controlled, and its bulb 61 is herein shown as being located in the return air duct II. The setting of this temperature controller is preferably such that its hot contacts or electrodes are bridged by the mercury in mercury switch 1 I when,the 'room or space temperature is approximately 75 F., whereas its cold contacts or electrodes are bridged when the' room or space temperature is '10 F. Such temperature controllers having appreciable differentials are well-known. The temperature controller 65 is shown in its cold position.

The dehumidifying coil valve 69 is controlled by a relative humidity responsive device generally indicated at 15., This device includes an arm 16 a double circuit mercury switch 82, the left-hand.

or opening electrodes of which are bridged by the mercury when the relative humidity of the space 0r room rises to some excessive value, such as sixty per cent, whereas the right-hand o r closing electrodes thereof are bridged by the mercury at some lesser value o f `relative humidity.

` Steam is supplied to the heating coil 2| and to the steam operated cooling means 45 by a steam boiler which is shown as fired by a gas burner (not shown) that is supplied by gas through a pipe 86. The now of gas through gas pipe 86 is controlled by an electrically operable gas valve 81. Weather to heating coil-2| through a heating coil valve 88 by means of pipes 89 and 90. This steam, after flowing through the heating coil 2|, isV returned to the' boiler 85 inany of the usual manners. The boiler 85 further supplies steam to the secondary ejectors 48 and 49 during warm Weather through an electrically operable valve 9| by means of pipes 89, 92, 93, 94, and 95. Steam is likewise supplied to the primary ejector 46 by the boiler 85 during warm weather through an -electrically operable valve 96 by means of pipes 89, 92, and 91. v

The condensate from the primary condenser 41 is returned to the boiler B5 by a circulator |00 that is driven by an electric motor |0l. Condenser water is supplied to the primary condenser y 41 and to the inter and after condenser 50 through a condenser water valve |02 by means of pipes |03, |04, and |05. This condenser water can be obtained in any of the usual manners, such as from the city water supply, a cooling tower, etc.

'I'he secondary ejector valve9l, the condensate This boiler 85 supplies steam during cold motor |0I, and the condenser valve |02 are controlled by a pressure switch generally indicated at I I0. This pressure switch I |0 includes a bellows whichis connected to the pipe 89. The bellows I|| operates an larm ||2 which is pivoted at ||3 and carries'a double circuit mercury switch ,||4. v'The mercury switch II4 is provided with The secondary ejector valve 9| and the condenser water valve I02 are directly controlled by the pressure switch IIIJ, whereas the .condensate motor I0| is controlled indirectly by the pressure switch I|0 through a relay H5. This relay ||5 includes a relay coil ||6 which, when energized,

attracts an armature I l1 that moves a switch arm |I8 into engagement with a contact H9.

The primary ejector valve 96 is controlled by the conjoint action of a pressure switch |25 and a vacuum switchiIZB. 'Ihe pressure switch |25 includes a bellows |21 that responds to boiler Y pressure and is herein shown as connected to the pipe 91. The bellows |21 operates an arm |28 which is pivoted at |29 and carries a double circuit mercury switch |30. The arrangement is such that the high pressure contacts of the'mercury switch |30 are closed when the boiler pressure rises to twelve pounds, andthe low pressure contacts'are closed when the boiler pressure falls to eleven pounds. The vacuum switch |28 includes a bellows |3| that responds to the vacuum in the cooling unit and is herein shown as con- 5 nected to the inter and after condenser 58 by means of a pipe |32. The bellows I3I operates an arm |33 which is pivoted at |34 and carries a double circuit mercuryswitch |35. The arrangement is' such that the low pressure or high vacuum contacts in the right-hand end of the mercuryswitch are closed when the vacuum in the inter and after condenser falls to sixteen inches of mercury. AThe pressure switch |25 and vacuum switch |28 also control the chilled water 1g motor 54 through a relay |36 that includes a relay coil |31 which, when energized, attracts an armature |38 that in turn moves a switch arm' |38 into engagement with'a contact |40. Y During warm weather, the gas valve 81is controlled by a room thermostat and a pressure switch |45.' The room thermostat |45 includes a suitable temperature responsive element |41, herein shown as comprised of bimetal, that opgage a contact |48. The arrangement is such that contactarm |48 engages'contact |48 when the room or space temperature rises to some undesired high value, say 75 F., and disengages contact |49 at some slightly lower temperature. n The pressure switch r|48 includes a bellows |50 which responds to the pressure in boiler 85 and is shown as connected to pipe 88." Bellows |50 operates an arm I5| which is pivoted at |52 and carries a mercury switch |53. 'I'he arrangement s is such that mercury switch |53 is opened when the boiler pressure rises to fourteen pounds and returns to closed-position when the boiler pressure falls to twelve pounds. During warm weather, the gas valve 81 is additionally controlled by n a temperature controller |50 which includes a Abellows |8I ,that is connected to a bulb |82 by a tube |53. The bulb |82 responds to the temperature of the chilled water in the evaporator 5|. 'I'he bulb |52, bellows |5|, and connecting tube a |53 are charged with'the proper amount of .suit-l bellows |8| operates an arm |54 which is pivoted at |85 and carries a mercury` switch |55. The

arrangement ls such that mercury switch |88 '1 is normally closed, but opens if the temperature of thechilled water in the evaporatorI 5| falls to some'unde'sired low value,'say 35 F.

The' gas valve 81' is controlled during cold weather by a pressure switch |10 that includes 'boiler 85 and is shown as connected to the pipe 88.l The bellows |1I operates an arml |12 which is 'pivoted at |18 and carries a mercury switch |14. The pressure switch |10 is arranged to move mercury switch |14-thereof to closed position wheneverv the boiler pressure falls to two pounds,

the switch being open for all higher values of the boiler pressure. The gas valve 81 lis additionally controlled both inywarm and cold weather by means of a"boi1er water level responsive switch water level in boiler 85 becomes too low. The system of the present invention includes an automatic change-over mechanism by means 7g of which the system is controlled to provide a by outdoor temperature in the specific embodiment .l of the inventicm herein disclosed. This u change-over mechanism includes a relay |80 and erates a contact arm |48 which is adapted to en` able volatile fluid, as 'is usual in the art. The` x a bellows I1| which responds to the pressure in l|15 which moves to open Vposition whenever the.

cooling function or a heating function depending upon the demands, which demands are measured.

a temperature controller I8| The relay |88 includes a relay coil |82 which attracts an armature |83 when energized. When the relay coil |82 vis energized, armature |83 moves a switch arm |84 from engagement with a contact |85 and 'l into engagement with a contact |85. Similarly, switch arms |81 and |88 are moved into engagement with contacts |88 and |80 upon energiza- `tion of lrelay coil |82. 'I'he temperature cont-roller I8| includes a bellows |8I that is con l.

nected to a controlling bulb |82 by means of a tube |83, the'bellows, bulb, and tube being charged with a proper amount of suitable volatile fluid. The bellows |8| operates an arm |84 which is pivoted at |85 and carries a mercury switch |88. 1|

lThe-bulb |82 responds to outdoor temperature,

and the arrangement is such that mercury switch |85 is moved to closed position to energize relay coil |82 whenever the outdoor temperature rises to some high value, such as 75 F. and remains 'n lin closed .position until the outside temperature falls to some low value, such as F.

The blower motor i8 is controlled by a relay 200 that includes av relay coil 20| which, when energized, attracts an armature 202 and moves ,-25

a switch arm 203 into engagement with a contact 204. During certain phases of the operation of the system, the relay 200 is controlled in part by a temperature controller 205 which includes a bellows 208 that is connected to a controlling m bulb 201 by means of a tube 208. the bellows,

bulb, and tube being properly charged with fluid. Thebellows 205 operates an -arm 208 which is pivoted at 2|0 and carries a mercury switch 2| The temperature controller 205 responds to the 35 temperature of the conditioned air being delivered to the room or space, and its bulb 205 is herein shown as being located ,in the path of the air leaving the air conditioning chamber I0. The y arrangement is such that mercury switch 2I| moves to open position whenever the tempera- A ture of the conditioned air falls below some de sired minimum value, such as F.

Turningv now Ito Figs. 2 and 3 of the drawings, the mechanism-by which the mixingdampers, `|3 and |4,`the by-pass dampers 23, and the face dampers 22, as well as the heating coil valve 88 are controlled will be explained in detail.

The mixing dampers I3 and I4 are respectively' located in the return air duct and the outdoor or fresh air duct i2, being respectively pivoted at These mixing dampers I3 and I4 are inter-connected by means of a tie-.bar 222. The mixing dampers I3 and I4 are operated' by a l 220 aridl 22|.

motory mechanism generally indicated 'at 223 which includes a main operating shaft 224 that is provided with a crank 225 which is connected to the damper I4 by means of a tie-bar 228. A gear 221, which is secured to mainv operating which also carries a pair of armatures or rotors 23| and 232. '."Associated with amatures 23| and shaft 224, is connected to a motor pinion 228 so 232 are energizingor ileld .windings 233 and 234.

Energization. of the field windings 233v and 234 is controlled by a vbalanced relay which includes a pair of. similar relay coils 235 and 238 that cooperate to' position a single plunger or armaturey 231.

ducting connecting member 238. The switch arm 238 cooperates with a pair of spaced contacts 240 and 24|. The position of plunger 231 is addition- Armature 231 is connected to `\a 70 switch arm 238 by a non-magnetic and non-con- '1 ally controlled, under certain conditions, by a 1g -pair oi 'similar auxiliary relay windings 242 and can The position of plunger 231 is primarily ycon-1 trolled by a resistance type of outdoor thermovstat whichis generally indicated at 245 (see Fig.

3)'. 'Ihis outdoor resistance' type or potentiometer thermostat includes a helically coiled thermal element 246 which may be of the `usual bimetallic construction. One end of the thermal element 246 is fixed, either permanently or adjistably, at 2u, and its other ena operates a `torsion rod 248 which in turn carries a contact -arm 249. The contact arm 249 cooperates with fresh-air duct I2, and the adjustment is such that the contact arm 249 engages the effectivecenter of the resistance 259, as shown in Fig. 3, when the outdoor or temperature is 70 F. If the outdoor temperature rises to 80 F., then contact arm 249 moves to the extreme right-handl end of resistance 259. When the outdoor temperature falls to F., then contact arm 249 moves to the geometric center of resistance 250, and at 50 F. the contact arm 249 moves to a position substantially midway between the geometric center of resistance 250 and the extreme left-hand end thereof, whereas if the outdoor temperature falls to 40 F., the ycontact arm 249 engages the extreme left-hand endof resistance 250.

The energization of relay coils 235 and 236 is' also controlled, or rebalanced, by means of a balancing potentiometer including a resistance winding 253 which is adapted to be traversed by a contact arm 254 that s operated bythe main operating shaft 224. A rheostat includinga resistance 255 and a manually adjustable contact arm 256V is preferably associated with the outdoor resistance 250 for a purpose to be hereinaf` ter set out. Associated with the outdoor resistance 250 is also a resistance 251. `lThe resistance 251 is adapted to beshort-circuited ,by a temperature controller 258. This temperature controller 258 includes a bellows 259 which isl connected to a controlling bulb 260 by means of a tube 26|, the bellows, bulb, and tube being charged with the volatile fluid. The bellows 259 operates an arm 262 which is pivoted at 263 and carries a mercury switch 264 'I'his temperature controller 248 responds to-'the temperature of the room orfspace being controlled, and its bulb 260 may be conveniently located inthe return air -duct II. The arrangement is such that the mercury switch 264 is moved to closed posirtion when the room or space temperature rises` to some undesired high value, s uch as F., and

is open for all temperatures therebelow.

Low voltage electrical power is' supplied to the various relay coils and eld windingsby means of the low voltage secondary210 of a'step-down transformer 21| having a high voltage primary Aeach of the eld windings 233 and 234 is connected to one side of secondary 21|) by wires 213 lay winding 242 by means of wires 291 and 293.

pinion 320 through ysuitable reduction gearing -and 335. The energization's of relay windings 321 and 328 are controlled by a temperature con- 256 of the rheostat is connected to the left-hand end of control resistance 258 `luy a wire 282. The outer end of relay 'coil 236 is connected to the other end of balancing resistance 253 and to one end of resistance 251, through a similar pro- 5 tective resistance 2,83, by means of wires 254,

285, 296, and 281. This same end of resistance 251 is connected to one of the electrodes of mer- .cury switch 264 of temperature controller 253 by means of a wire 263. The other end of re- 10 sistance 251 is connected to the other electrode of and- 295. The other en d of field winding 233 is 2 connected to contact 240 through auxiliary relay' winding 233 by means of wires 295 and 296. Similarly, the otherv end of eld winding 234 is y connected to contact 24| through auxiliary re- The relay switch arm 233 is connected to the. other side of secondary 210 by wires 215 and 299.

The face dampers 22 are inter-connected by means of tie-bars 3|0,and by-pass dampers 23 are inter-connected by means of a tie-bar 3H. One of the face dampers 22 is connected to one of the by-pass dampers 23 by a tie-bar 3|2 so that all of the face and by-pass dampers are operated in unison. The face and by-passL dampers are adapted to be operated'by a motor mechanism generally indicated at 3|5. This motor mechanism includes a main operating shaft 3 i 6 that is provided with a crank 3| 1 which is connected to one of the laypass dampers 23 by a tie-bar 3|8. A gear-3|9 which is secured to the main operating shaft 3|6 is connected to a motor 32|. Motor pinion 329 is secured to a rotor shaft 322 which carries a pair of armatures or rotors 323 and 324. A pair of energizing or field windings 325 and 326 are associated with the rotorsv 323 and 324. Energization of the ield windings 325 and 326 'is controlled by a balanced relay mechanism that includes a pair of similar relay coils 321 and 328 which cooperate in the positioning or" a plunger or armature 329. The plunger or armature 329 positions a relay switch arm 330 through the medium of a non-magnetic and non-conducting connection 33|, the relay switch arm 330 in turn cooperating with a pair of spaced contacts 332 and 333. 'I'he position 0f plunger or armature 329 is additionally controlled by a pair of similar auxiliary relay windings 334 troller in the form of a potentiometer thermostat which includes a thermal actuator 345, herein shown as a cpiled bimetallic strip, that positions a control contact arm 34| which in turn cooperates witha control resistance 342. The control resistanc 342 is evenly wound about a suitable support (not shown). This potentiometer thermostat responds to the room or space temperature'and may be conveniently located in the return air duct as shown. The calibration is such that the control contact arm 34,| engages the extreme right-hand end of control/resistance 342 when the room or space temperature is'10" 1". and engages the extremeleft-handfend of-thls control resistance when the Aroom'or space temperature. falls to 68 yus F., these limits, of course, being merely exemplary. The energizations of relay windings anced by a balancing potentiometer which-includes a balancing resistance 333 and a balancing contact arm 333 cooperable therewith which is secured to the main operating shaft 3|3.

Low voltage electrical power is supplied to the motor mechanism 3|5 by means of the lw vo'ltage secondary 333' of a step-down transformer i having a`hlgh voltage primary 352 that is connected to suitable line wires. The relay coils 321 and 328, in series, are connected across the secondary 353 by means of wires 355,353, 351, 353, and 353. balancing resistance 333 are connected in parallel across the secondary 353 through similar protective resistances 333 and 33| by means of wires 355, 353, 332, 333, 333, 335, 338, 331, 383, and 353. The junction of relay coils 321 and 328 the control contact arm 33|, and the balancing IContact arm 333 are interconnected by means of wires 333, 313, and 31|. One end `oi' each of the field windings 325 and 323 is connected to one side of secondary 353 by means of wires 353, 383, and 312. The other end of field winding 325 is connected lto contact 332 through auxiliary relay .winding 333 by means of wires 313 and 313. Likewise, the other end of eld winding 323 is connected to contact 333 through auxiliary relay winding 335 by means of wires 315 and 313. The relay switch arm 333 is connected tothe other si1de of secondary 353 by means of wires 355 and 3 1.

The main operating shaft 3| 3 of motor mechanism 3| 5 carries a cam 333 which is provided with a closing portion :si and an opening p'ortion 332. i A cam follower 383 which is pivoted at 333 cooperates with the closing and openingportions of cam v333 and f carries a mercury switch 335 which is provided with closing and opening electrodes for cooperating in the control of the heating coil -valve 33 in a manner to be subsequently enplained.

Operation of the face and Inl-pass dampers and the heating coil valve Referring to Fig. 2 of the drawings, the outdoor temperature has been 'at or above 75 F. but has dropped to substantially 73 F. so that the mercury switch |33 'of the change-over thermostat |3| is in closed circuit position. lRelay coil |82 of the change-over relay |33 is therefore energized as follows: line 333, mercury switch |33, wire 33|, relay coil |32, and line 332. Switch arms |33, |81, and |33 are therefore engaged with their respective contacts |33, |33, and |33,

,l and switch arm |33 is disengaged from contact The indoor temperature is likewise about '70 F. or slightly thereabove so that control contact arm 33| is engaged with the extreme right-hand end of control resistance 332, and balancing contact finger is engaging the extreme right-hand end of balancing resistance 333. Relay coil 321 is therefore substantially short-circuited by a circuit which is as follows: relay coil/321, wire 333, wire 313, thermal element 333, control contact arm 33|, wire 332, protective resistance 333, and wire 331 to the other side of relay 321. Likewise, with the parts inthe position shown, relay coil 323 is substantially short-circuited by a circuit as-follows: relay coil 323, wire 333, wire 31|, balancing contact arm 333, wire 335, wire 333, protective resistance 33|, wire 331, wire 353, and

321 and 323 are adapted to be,bal.

'coils 321 and 328 llay switch arm 333 is intermediate contacts 332 The control resistance 332 and the,

above described energizing circuit for relay coil wire 353 to the other side of relayl coil 328. The inclusion of protective 'resistances333 and 33| prevents the complete short circuiting of relay when the control contact finger 33| and the balancing contact 333 are in 5 the extreme positions shown or in the opposite extreme positions. Relay coils 321 and 328 are therefore equally energized, and the plunger 323 assumes the central position shown, wherein reand 333. Field windings 325 and 323 are therefore both deenergired so that rotor shaft 322 and main actuating shaft 3|3 are stationary. The by-pass dampers 23 are both open, and the face dampers 22 are all closed, thereby requiring that all air flowing into the air conditioning chamber |3 must pass through the by-pass chamber 23.

Cam follower 383 is engaged with the closing o portion 38| of the cam 333 so that mercury switch `385 has its closing electrodes or left-hand electrodes closed. Heating coil valve 83 is closed, r however, irrespective of the condition of mercury switch 385 by a circuit as follows: secondary 333 of a transformer 333, wire 335, switch arm |83 and contact |83 of change-over relay |83, wire 333, wire 331,- heating coil valve 88, and wire 333. to the other side of secondary 333. As a result, no steam can flow to the heating coil 2|.

As long as the outdoor temperature does not fall below 70 F., the room 'or space temperature will also remain at or above 70 F. so that control contact arm 33| will remain in engagement with the extreme right-hand end of control resistance 332, and the face and by-pass dampers will remain in the positions shown. Now if the outdoor temperature falls slightly, mercury switch |33 of the change-over temperature controller |3| will move to open position, and the |32 of the change-over relay |33 will be interrupted. Switch arms |83, |81, and |88 will therefore move from engagement with contacts |83, |83, and |33,.and switch arm i 33 will move into engagement with contact |85. When this outdoor temperature drop rst takes place, the indoor temperature probably will not fall for at least a short time so the motor mechanism 3|5 will remain in'the position shown. Movement of switch arm |83 into engagement with contact |85 does not open the heating coil valve 83 but, in fact, places the control of this valve upon the mercury switch 385. As long as mercury switch 335 remains in the position shown, there will be a closing circuit for the heating coil valve 33 which is as follows: secondary 333 of transformer 333, wire 335, switch arm |83, contact |35, wire 333, closing contacts of the mercury switch 335, wire 33|, wire 331, valve 88, and wire 338 to the other side of secondary 333.

Now if the room or space temperature falls lsomewhat, control contact arm 33| will move will be established as follows: secondary 353 of transformer 35|, wire 355, wire 311, relay switchl arm 333, contact 332,'wire 313, auxiliary -relayl winding 333, wire 313, field winding 325, vwire 312, wire 333, and wire 353 to the other side of secondary 353. Energization of auxiliary relay winding 334 causes an additional pull to be exerted upon plunger 329 tending to move the same toward the right, whereupon the original light contact pressure between relay switch arm 338 'and contact 332 will be increased whereby to assure a good firm contact therebetween.- Energization of field winding 325 causes rotation of rotor 323' inv a counter-clockwise direction, looking upwardly, whereupon main actuating shaft 3|6 will be rotated in the same direction. Balancing contact finger 344 thereforemoves slowly along balancing resistance 343 toward the left-hand end thereof 'until the voltage drop across relay coil 32E-is made slightly larger lthan the voltage drop across relay coll 321 and returns plunger 329 to its central position,` moving relay switch arm 330 from engagement with contact 332, whereupon field winding 325 is deenergized. During this time, crank SI1 is ro` tateda small amount -in counter-clockwise direction, whereupon by-pass dampers 23 revolve a small amount in,the same direction so as to -partially close oif by-pass passage 28. Similarly, ,the face dampers 22 are rotated a small amount Alill, and wire '338 to the other side of secondary 3/93. Opening of the heating coil valve 88 permits the passage of steam to the heating coil 2| so that the small amount of air passing through the heating chamber i3 is raised in temperature `before being delivered to the room or space to be heated.

As it becomes.' colder outdoors, or if for any other 'reason the room or space temperature should drop further, control contact arm 33| moves further along control resistance 342 to" ward its left-hand end with the result that eld winding 325 is again energized, and main actuating shaftI 3|@ is moved further in counterclockwise direction. If the room or spalce temperature drops to 68 F., the control contact Varni 34| will engage the extreme left-hand end of' control' resistance 332, whereupon relayl coil 328 is substantially short-circuited by the following circuit: relay coil 328, wire 389, wire 318,

thermal element 348, control contact arm 33|, wire 364, wire 363, protective resistance 38|, wire .361, wire 368, and wire 353 to the other side of relay coil 328. Main actuating shaft 3|6 will A"therefore/be rotated in counter-clockwise direction until balancing contact finger 364 moves to the extreme left-hand end of balancing resistance 343, whereupon relay coil 321 will be substantially short-circuited as follows: relay' coil 321, wire 369, wire 31|, balancing contact arm 384i, wire-333,- protectiveresistance 388, and wire- 351 to the other` side of relay coil 321. Plunger 329 will therefore assume its central position as contact varm 34| and balancing contact arm 333 l AS a result, crank 3 i1 will have been moved through shown in Fig. 2 of the drawings, but control will be i'n their opposite extreme positions.

a complete half revolution, whereby the by-pass dampers 23 will be completely closed to ,prevent ams-,35e

the flow of any air whatsoever through the bypass chamber 20, and the face dampers 22 will be completely opened toi permit all of the air passing to the air conditioning chamber l0 to pass through the heating chamber i9 and over the heating coil 2|. .At this time, the cam follower 383 will still be engaged with the opening portion 382 of the cam 380. I

Whene/ver the room temperature rises, control contact arm 34| will move along control resistance 342 toward the .right-hand end thereof, L

whereupon the voltage drop across relay coil 328 will become suiliciently greater than the voltage drop across relay coil 321 to cause plunger 329 to move suiiiciently toward the left to bring relay switch arm 330 into engagement with contact 333.v This establishes a series circuit through the auxiliary relay vwinding 335 and the eld winding 826 which is as follows: secondary 350, wire 355, wire 311, relay switch arm 330, contact 333, wire 318, auxiliary relay winding 385, wire '315, `field winding 328, wire 312, wire 388, and

wire 359 to the other ,side of secondary 3540.' Energization of. auxiliary` relay winding 335 exerts a`n additional pull on plunger 329 toward the left, whereby relay switch arm 330 is brought into firm engagement withcontact 333. Energization of field winding 323 causes rotation/of motor rotor 324 in a clockwise direction,looking upwardly, whereupon main actuating shaft 3|8 is likewise rotated in a clockwise direction. -Balancing contact arm 344 therefore moves along balancing resistance 343 toward the right-hand end thereof until the voltage 'drop across relay winding 321 is made sufllciently greater than the voltage drop across relay winding 328 to return the plunger 329 to its central position whereupon field winding 328 is` deenergized. During this time, crank 3|1 is rotated in a clockwise direction partially to open, or open further, the by-pass dampers 23 andpartially to close, or close further, the-face dampers 22.

In this man'ner, whenever thesystem is on summerr operation by reason of mercury switch |96 of the change-over temperature controller |8| being closed, the heating coil Vvalve 88 is closed irrespective Yof the room or space temperature. However, whenever the outdoor temperature is s umciently lowM so that the mercury switch |95 is open, the heating coil valve 88 is controlled by the thermal element 340 through the medium of the motor .mechanism 3|5 and Operation .of the mixing dampers Operation if the mixing,l dampers i3 and i4 is controlled by the potentiometer outdoor temperature controller 245 through motorvmechal nism 223 in a manner/very similar to the-manner in which the face and loy-pass dampers 22 and 23 are ycontrolled by the indoor potentiometer controller through the motor mechanism 3|5. With the parts in the position shown, the outdoor temperature is substantially '10 F. so that control contact arm 249 is engaged with the effective center of the resistance 258. The rheo- 7g Atior1,'and mixing damper I3 is rotated in countercentral position and deenergize field winding 233. During this time, mixing damper i4 is rotated in clockwise direction toward its horizontal posiclockwise direction toward its vertical position.

When the outdoor temperature has returned to 70 F., the parts will resume the position in which they are shown in Fig. 2 of the drawings. Upon continued outdoor temperature fall, accompanied by continued counter-clockwise rotation of main actuating shaft 224, mixing damper |4 will continue rotating in a clockwise direction and towardits vertical position. Mixing damper I3, after reaching its vertical position, will begin rotating in a counter-clockwise direction toward its horizontalposition. When the outdoor temperature falls to 40 F. the relay coil 235 will be shortcircuited, except for the protective resistance 211 and the effective portion of rheostat resistance n 255. Balancing contact finger 254 will not, therefore, move to the extreme left'end of balancing Aresistance 253 in rebalancing the voltage drops across relay windings 235 and 235. Mixing damper i4, therefore, is not moved to its complete vers tical position, nor is mixing damper I3 moved to its complete horizontal position. In thisrmanv ner, a predetermined minimum. supply of outdoor airis furnishedl to the air conditioning chamber I0, regardless of -how low the outdoor temperature falls. The amount of this predetermined minimum outdoor air flow may be adjusted by adjusting the effective portion of rheostat resistance 255. v

It -will therefore be seen that at normal or in- 35 termediate outdoor temperatures, 70-,F. in the disclosed arrangement,a full flow of outdoor air is taken into the air conditioning chamber I0, and no air is taken thereinto from the room or space being controlled. Then if the outdoor temperature either rises above or falls below this intermediate value, the amount of outdoor air is decreased, and an increasing amount ofA room or space airis allowed to pass to the air conditioning chamber |0, but this rate of change per degree change in outdoor temperature is not the same for temperatures` above and below 70 F. by rea.-

` son of the tapered nature of the resistance winding 250. Furthermore, there is provision by which definite predetermined minimum flows of outdoor air are taken into the air conditioning chamber I0 for ventilation purposes, irrespective of how high or how low the outdoor temperature becomes. When 'the outdoor temperature becomes excessive, however, if the indoor temperature likewise becomes excessive, then this minimum inflow of outdoor air is prevented by operation of the temperature controller 258. The minimum flow of outdoor air takeninto the air conditioner durring coldweather can be varied by manual adiustment'of rheostat arm 258.y

It will be noted that the automatic changeover mechanism plays no part-whatsoever Iin the control` of the mixing dampers I3 and |4, these mixing dampers being controlled entirely both in cold and warm weather in accordance with changes in outdoor temperature, except for the abnormal control function furnished. by the temperature controller 258, whereby thev minimum supply of outdoor air during hot weather iseliminated if the room or spacetemperature becomes excessive.

Operation of the'complete system Power is supplied to certain parts off-the system by line wires 420 and 42|, the 'lattery of which,

auaase door alrto the air conditioning chamber i0, and

the face and by-pass dampers 22 and 23 are posi- -tioned, to direct this full flow of outdoor' air vthroughthe by-pass chamber `\20, all in the manner heretofore set out. Also, the heating coil valve 8 is closed.

The blowerk motor I6 is energized whenever relay coil is energized, the blower motor circuit being as follows: line wire 423, contact 204, switch arm 2 03, wire 424, blower motor I5, and line wire 425. With the wiring arrangement shown, the relay coil 20| is constantly energized when the system' is operating on the warm weather cycle. This energizing circuit for relay coil 20| is as follows: line wire 420, wire 428,

'switch arm |81, contact |88, wire 421, wire 428,

relay coil 20|, and ground 422. While the blower motor i8 has been shown as constantly energized during the warm weather cycle, it will be appreciated that in some instancesit may be desirable to operate the blowermotor I6 only when there is a demand for cooling, and, in certain installations, it may be further desirable to prevent the operation of the blower motor |8, as weil as certain other of the lparts, during the night or other .hours when the room or space to be controlled is Vgenerally unoccupied. y

The relative humidity of the room or space to be controlled is between forty and sixty per cent. Mercury switch 35 of humidity controller l32 is therefore open, and the water valve 3|, which controls the flow of water-to the spray 25, is deenergized. Also, the closing contactsof mercury switch 82 of the humidity controller 15 are closed, so that a closing circuit for'dehumidifying valve 50 is established as follows: secondary 430`of, a

transformer 43|, wire 432, closing contacts of,y the mercury switch 82, wire 433, dehumidifying coil valve 59, and wire to the other side of' `secondary 430.

The boiler pressure is less than two pounds, so the mercuryswitch |14 of two-pound pressure switch |10 is closed. The water level in the boiler is suiliciently high. so thatI the water level responsive switch |15 is also closed, and the temperature of the chilled water` in the 'evaporator 5| is above 35 F., so that the mercury switch I65of the freeze control |5015 also closed. With the wiring arrangement shown, gas valve 8 1 is therefore energized as follows: line 420, wire 428,

wire435, wire 435, mercury switch |14, wire 431, wire 438, low water cut-off switch |15, wire 439, freeze control switch |86, wire 440, gas valve 81, and wire 44| to ground 422. The,pressure switch |18 will therefore operate to maintain ay steam pressure of two pounds in the boiler 35, irrespective of whether the system is operating on the warm or cold weather cycle. In some instances,;it may be desired to operate the boiler .onlyI to vmaintain a constant minimum pressure of two pounds during the cold weather cycle, `in which event the'wire 435 may be omitted and replaced by'a wire which is connected to a contact that is adapted to be engaged byI switch arm would not be operated during the warm weather boiler pressure of heretofore described. A rise in outdoor temperature will result in a rise in indoor temperature, and when the indoor temperature reaches some undesired high value of say 75 the contact arm |48 of the room thermostat |45 will move into engagement with contact |48, whereby gas valve 81 will be energized irrespective of the wiring to the two-pound pressure switch |10. This en-l` e'rglzing circuit for the gas valve 81 is as follows: line 420, wire 428, wire 435, wire 445, switch arm |88, contact |80, wire 448,'thermal element |41, contact arm |48, contact |48, wire 441, mercury switch |53 of the fourteen-pound pressure switch wire 481, high pressure contacts of mercury Vswitch |30, wire 488, wire 412, relay coil |31, and wire 413 to linewire 41|.

Opening of primary ejector valve 85 admits steam to primary ejector 48 whereby the temperature of the water in evaporator 5| is reduced.

Energization of relay coil |31 energizes circulatlng motor '54 as follows: line 415, switch arm |38,

|48, wire 448, wire 438, low.water cut-oil' switch |15, wire 438, freeze control switch |86, wire 440, gas valve 81, and wire 44| to ground'422. Energization of the gas valve 81 operates to supply heat to the boiler 85, whereupon the steam pressure thereof will be raised.

When the boiler pressure reaches nine pounds, the pressure switch ||0 will operate mercury switch ||4 to close the high pressure electrodes thereof, whereby opening circuits for secondary ejector valve 8| and condenser water valve |02, as well as an energizing circuit for relay coil ||8, are established. The circuit for secondary ejector valve 8| is as followsrline 450, high pressure con,-

.tacts of mercury switch ||4, wire 45|, wire 452,"

wire 453, secondary ejector valve 8|, wire 454, andwire 455 to line wire 458. 'I'he opening circuit for condenser watervalve |02 is as followsz' line 450, the high pressure contacts; of mercury switch ||4, wire 45|, wire 452,wire 451, condenser *water valve |02, wire 458, wire 455, to line wire -inter and after condenser 55.v Enersization of 458. The energizing circuit for relay coil ||5 isas follows: line 450, the high pressure contacts of mercury vswitch H4, wire 45|,l wire 455,4

relay coil ||5, and wire 450 to li-ne 458.-

vOpening oi' secondary ejector vvalve 5|- admits steam to the'secondary ejector-s 48" and 45, and

openingA of condenser water valve |52 admits' cooling water to the primary condenser 41 and mercury switch |35 ofvvacuumswitch |28- soon" close. Continued operation of the Iboiler causes the steam pressure .to rise, \and when it reaches twelve pounds, the highv pssure contacts oi. mercury switch |38 of the pressure switch |25 will also close, whereupon an opening circuit for primary` ejector valve 85 is established, and an energixlnglcircuit for the relay coil |31 ofthe chilled water circulating motor relay |35 isclosed.

'Ihis opening circuit for primary ejector valvel 58 is as follows: line' 455, wire 455, high vacuum or` low pressure contacts of mercury switch |35, wire 451, high pressure contacts of mercury switch |30, wire 455, wire 458. primary ejector valve 88, and wire 415 to line wire 41|. The energizing circuit forfrelay coil |31 is as follows'gline wire 485,.wire 35 488,I high vacuum contacts of mercury switch |35,

. with its contact |48, thereby deenergizing gas When the room or space temperature formerly rose to '15 F., the temperature controller 85 operated its mercury switch 1| to close the circuit through its opening contacts or high temperature contacts, whereupon an opening circuit for cooling coil valve 58 was established as follows: secondary 480 of step-down transformer 48 wire 482, high temperature contacts of mercury switch 1|, wire 483, cooling coil valve 56, and wire 484 to the other side of secondary 480. As a result, the water in evaporator 5| is chilled and is circulated to the cooling coil 24 by means of circulator 53. The airo passing through the conditioning chamber I0 is therefore reduced in temperature in an attempt to restore the room temperature to the desired value. If the boiler pressure should reach fourteen pounds, the pressure switch |45 would open its mercury switch |53 to deenergize the gas valve 81. 'I'his mercury switch |53 would again close when the boiler pressure became reduced to twelve pounds. If for any reason the vacuum in the inter and after condenser should become less than the desired sixteen inches of mercury, i. e. if the vacuum should become fourteen inches of mercury for example, the mercury switch |35 of vacuum switch |25 will return to the position shown in Fig. 1 of the drawings to close the lefthand contacts of mercury switch |35 andopen the right-hand contacts thereof; `This deenvergizes relay coil |31, and establishes a closing circuit ior primary ejector valve 88. The closing circuit for primary eiectorvalve 55 is as follows: line 455,'wire 588, low Avacuum contacts of mercury switch |35, wire 485wire 488, primary ejector valve 85. wire 415, and line 41|. Similarly, ii'

the' steam pressure should fall below eleven pounds, the low pressure contacts of mercury" switch |38 will be reclosed, as shown in Fig. 1, whereupon .the enerlilins circuit for relay coil |31 will be interruptedg'and a closing circuit for primary ejector valve-85 will be established ir,-

respective of the condition of vacuum switch |28.

This closing circuit for primary ejector valve 88 is as follows: line 485`wire 481, low pressure contacts of mercury switch l38, wire 485, primary ejector valve 55, wire 415, and line 51|.`

In 'this manner, operation of' the primary elector ,to cool the waterinjevaporator 5| is prevented'whenever the steam pressure becomes toov lowand whenever there is insumcient vacuum in the inter and after condenser 58. f

I! the roomtemperature is thus lowered below 35? F., the mercury switch 1| oi'y temperature controller 55 returns to the position shown wherein its low temperature contacts are closed and establishes a closing circuit forv cooling coil valve 55 as follows: secondary 458, wire 482, low temperature contacts oi mercury switch 1 wire 485,

cooling coil valve 55; and wire 484 to the other side of secondary 480.` This lowering of the room temperature also moves contact blade |48 of the temperaturev controller V|45 from engagement valve 81. The steam pressure therefore quickly falls below eleven -pounds, returning pressure -switch |25 to the position shown, whereuponv circuit described above, and the relay coil |31 will be deenergized to interrupt the energizing circuit for circulator motor 54. The steam pressure will continue to drop, and when it reaches seven pounds, the pressure switch I I0 will return to the position shown in Fig. 1, whereupon relay coil ||6 will be `deenergized to interrupt the energizing circuit for condensate motor |0|, and closing circuits for secondary ejector valve 9| and condenser water valve |02 will be established. The closing circuit for secondary ejector valve 9| is as follows: line 450, low pressure contacts of mercury switch |4, wire 490, wire 49|, secondary ejector valve 9|, wire 454, wire 455, and line 456. The closing circuit for condenser water valve |02 is as follows:` line 450, low pressure contacts oi mercury switch H4, wire 490, wire 492, condenser Water valve |02, wire 458, wire 455, and line 456. v

If the temperature of the chilled water in the evaporator 5| is reduced to the value of 35 F. during a demand for cooling, 'the mercury switch |66 of the freeze control |60 will be moved to open position and interrupt the energizing circuit for gas valve 8?. sure will soon fall in the` manner hereinbefore described so as to prevent further operation ofthe steam jet ejector until the chilled water temperature rises to a safe value.` This freeze control' is purely a safety control, and ordinarily is not called upon to operate.

Whenever the relative humidity in the room orspace becomes excessive, expansion of the humidityresponsive element i8 causes the opening or left-hand electrodes of the mercury switch 82 to be closed, whereupon the dehumidifying coil valve 59 is opened by completion of the following open ing circuit therefor: secondary 430 of transformer 43|, wire 632, mercury switch v82, wire 490, dehumldifying coil valve 59and wire 434 to the other side of secondary 430. Opening oflthe dehumidifying coil valve 59 allows chilled water to now tothe dehumidifying con 2e inthe' event the cooling apparatus andthe circulator aie in operation. It will be noted that water of the same temperature issupplied to the cooling coll 24 and dehumidifying coil 26. While each of these coils will probably operate both to cool and dehumidify to a `certain extent, 'by' proper coil .de-

l,sign the cooling coil will operateprimarily to fcool, and the dehumidifying coil will operate primarily as a dehumidifying means.

During the warm weather operation, if the relative humidity should become too low, the humidity responsive element :i6` will contract sumciently to close the circuit through mercury switch 35, whereupon spray water valve 3| isen` ergized as follows: line 420, wire 426, switch arm .mum iiow position, and if the room temperature becomes excessive so as to close mercury switch 264, then the mixing damper |4 will be completely closed as hereinbeforedescribed.-

Whenever the outdoor temperature falls below '70 F., the change-over temperature controller |8| moves its mercury switch |98 to open circuit position, whereupon relay coil |82 of the change- Vns over relay |80 is deenergized. Switch arms |84,

As a result, the boiler pres- |81, and |88 thereiore'move from engagement with contacts |88, |89, and |90, and switch-arm |841movesvinto engagement with `contact |85. In this manner, the constant venergizing circuit' for fan motorv relay 200 is interrupted, and the heating coil valve 88 is placed under the control of the mercury switch 385 'of the motor mecha- ,nsm 3|5vas heretofore explained.

The gas valve 81 is then operated under the control of the two-pound pressure switch |10.by

one or the 'other' of the. circuits hereinbefore pointed out so as lio-maintain a minimum steam pressure of two'pounds. The fan motor relay 200 is energized at all times. provided the temperature of the air delivered from the air `conditioningchamber |0 to the room or space being controlled is vsufficiently high, say 75 F. This energizing circuit for the fan motor relay is as follows: line d20,v wire 485, mercury switch 2|l of temperature controller 205, wire-496,. wire 69| wire t28, relay coil 20|, and ground 422. Also, energization of the spray water valve 3| is dominated bythe temperature controller 205 during the cold weather operation, the circuit being as follows: line 420, wire 495, mercury switch 2li, wire 096, wire 492, mercury switch 35, Wire 493,

t spray water valve 3|, and wire 494 to ground From the foregoing it will be evident that the lsystem ofthe present invention is completely automatic and serves to supply heating or cooling as needed, and particularly according to changesyin outdoor temperature.. It is particularly to be noted thatx the\changeover temperature controller |8| operates .on a relatively wide differential, herein set out as 5 F., thereby preventing the changing over from heating to cooling upon minor outdoor temperature changes. Under some conditions it may be desirable to adjust the change-over temperature controller IBI to operate Aon a still-wider dierential. r

The system -of the present invention vfurther provides means by which the ow of steam either to the heating means or cooling means is selectively controlled in accordance with the demand for heating or cooling.` The invention also in cldes many other features of novelty,I many of which could be modified or rearranged without departing from the invention, and we therefore intend to be limited only by the 'scope of the .appended claims.

We claim: 1. A system of the'class, described, comprising,

in combinatlom circulating means for circulating outdoor air to a space the temperature of which it is desired to control, damper means associated with the circulating means and operative to. vary the volume of outdoor air supplied to said space, means including a thermostat responsive to the outdoor air temperature in control of said damper means and operativevto permit a maximum volume of outdoor air to be -supplied to said space when the outdoor temperature is at a desired normal and to reduce theV `.means including a thermostat responsive to the space temperature additionally controlling said damper means and operative to discontinue completely the supplying of outdoor air tothe space if the space temperature rises above a predetermined high value.

2. A system of the class described, comprising in combination, circulating means for circulating outdoor air to a space the temperature of which i it is desired to control, damper means associated with the circulating means and operative to varythe volume of outdoor air supplied to said space, means including a thermostat responsive to the outdoor air temperature in control oi said damper means and operative to permita maximum volume of outdoor air to be supplied to said space when' the outdoor temperature is at a desired normal and to reduce the volume of outdoor air supplied to the space to a predetermined minimum ii the outdoor temperature rises to a predetermined high value, cooling means for cooling the space, and means including a thermostat responsive to the space temperature which operates the cooling means ii the space temperature rises above a predetermined value and which operates said damper means to discontinue completely the supplying of outdoor air to said space if the space temperature rises to a still higher value,

3. In combinationdamper means in control of the supply of loutdoor air to a space to be controlled, means including-an outdoor temperature responsive thermostat associated with the damper means for operating the same to permit the supplying of a maximum volume of outdoor air to said space when the outdoor temperature is at a desired normal value and for gradually reducing the supply oi' outdoor air as the outdoor temperature rises until the supply of outdoor air reaches a predetermined minimum which is then maintained upon further increase in the outdoor temperature, and means including a thermostat responsive to indoor temperature for operating said damper means to discontinue the supply oi outdoor air to said space when the space temperature rises to some predetermined high value.

4. In combination, damper means in lcontrol of the supply of outdoor air to a space to be controlled, means including an outdoor temperature responsive thermostat associated with the damper means for operating the same to permit the supplying of a maximum volume lof outdoor air to said space when the outdoor temperature is at a desired normal value and for -gradually' reducing the supply of outdoor air as the outdoor temperature rises until the supply of outdoor air reaches a predetermined minimum which is then maintained upon'further increase in the outdoory temperature, cooling means for cooling the space, and means including a thermostat responsive-to the space temperature for operating the cooling means when the space temperature rises to a given value and for operating the` damper means to discontinue completely the supply of outdoor air if the space temperature rises to a still highe value. l

5. In combination, damper means in control of the iiow of outdoor air to a space to be controlled, means for cooling the space, means for heating the space,- space temperature responsive means which operates the'heating means when the space temperature falls to one value and which operates the cooling means when the space temperature rises to a higher value, and means responsive to outdoor temperature operative selectively to place said space temperature responsive means in control oi' thheatingor cooling means and to operate said damper means to per- ;mit a supply of outdoor air to the space when the outdoor temperature is at some selected intermediate value and to reduce the supply of outdoor air to the space if the outdoor temperature rises above or falls below said selected value.

' 6. In combination, damper means in control of the flow of outdoor air to a space to be controlled, means for cooling the space, means for heating the space, space temperature responsive means which operates the heating means when the space temperature falls to one value and operates the cooling means when the space temperature rises to a higher value, means including an outdoor temperature responsive thermostat arranged serises to predetermined values, and means including a second outdoor temperature responsive thermostat for operating said damper means to provide a maximum supply of outdoor air to said space-when the outdoor temperature is at some selected intermediate value and for gradually reducing the supply of outdoor air as the outdoor temperature rises above or falls below said selected value.

7. In combination, a boiler, a heating coil connected thereto for heating a space, a heating valve controlling the ow of fluid from the boiler to the heating coil, steam operated cooling means for cooling the space, a cooling valve in control of the ow of steam from the boiler tothe cooling means, a steam pressure responsive device operative to open the cooling valve when there is a predetermined steam pressure in the boiler, means including space temperature responsive mechanism for operating said boiler to produce' sufficient steam pressure to cause opening of the cooling valve on a demand for cooling and for operating the boiler and opening the heating valve when heating is necessary, and means including an outdoor temperature responsive thermostat for selectively permitting such control of said valves by said last-named means.

8. In combination, an air conditioning unit including a return inlet, an outdoor inlet and an outlet, mixing damper means for controlling the proportions of return air and outdoor air taken into said conditioner, means responsive to outdoor temperature controlling the mixing damper means to provide for the taking into said conditioner of a maximum amount of outdoor air when the outdoor air temperature is at a desired normal value and for reducing the amount of outdoor air taken into said conditioner to a minimum when the outdoor temperature rises to some maximum eration when-the space temperature rises to one value and for operatingthe mixing damper means to prevent the taking in of any air to the conditioner if the outdoorl temperature is at said maxi-A mum value and the space temperature rises to a second value.

9. In combination, a conditioner including an outdoor air inlet and an outlet communicating with a space to be controlled, damper means in control of the outdoor air inlet, outdoor temperature responsive means controlling said damper means to permit a maximum iiow of outdoor air to said conditioner when the outdoor temperature is moderate, gradually to decrease-the supply of outdoor air to a predetermined minimum as the 'loA outdoor temperature rises to a predetermined high value and to maintain said minimum supply it the outdoor temperature rises -till higher, a cooling coil in said conditioner for cooling the air therethrough, steam operated cooling meansoperative to supply cooling uicl tothe cooling coil, a boiler for providing steam for the cooling means, and space temperature responsive iii means operative to 'place said boiler in operation when the space temperature rises to a iir'st value and to operate the damper means to interrupt completely the tlow ot outdoor vair to the conditioner it the space temperature rises to a second higher value.

10..In combination, an air conditioner including an outdoor air inlet and an outlet which communicates with a space to be cooled, damper means in control of the flow of outdoor air to said conditioner, means including` a temperatureresponsive thermostat which operates the damper means to provide a maximum flow of outdoor air through the conditioner whenthe outdoor temperature is moderate and which gradually reduces the ilow of outdoor air as the outdoor temperature increases, avcooling coil in the conditioner for cooling the air passing therethrough, a dehumidifying coil in the conditioner for del humidifying the air passing therethrough, a cooling coil valve, a dehumidifying coil valve, means including a space temperature responsive thermostat operative to open the cooling ccil valve onI a demand for cooling, means including a space relative humidity responsive device operative to open the dehumidifying valve if the space relative humidity becomes excessive, and a steam operated cooling unit for supplying chilled water to the cooling and dehumidifying coils.

1l. In combination, a temperature changer, means for passing air over the temperature changer, damper means for varying the volume of air passing over the temperature changer, mo-

tor means, means including a space temperature responsive thermostat operative to cause positioning of the motor means in a plurality of positions in response to space temperature changes, connections between said motor means and damper means by which said damper means is variably positioned to proportion the iiow of air over the temperature changer, electrical means in control of the temperature changer, a switch in conmotor means, means including a space temperature responsive thermostat operative to cause positioning of the motor means in a-plurality of positions in response to space temperature changes, connections between said motor' means and damper means by which said damper means is means becomes excessive.

ventrasse Virll'iblirv positioned to proportion the ow of air over thel temperature changer, valve means in contralor the 'temperature changer, a controller in control of the valve means, connections between the controller and motor means arranged to operate the controller when the motor`means is in only one of its extreme positions, and outis above a. predetermined value, and means re-` sponsive tov a condition of the inside air for operating said air forcing means independently of said outside temperature responsive means.

14. A system of the class described, comprising, in combination, circulating means for circulating outdoor air to a space the conditions of which it is desired to control, damper means associated with the circulating means and operative to vary the volume of outdoor air suplied to said space,

`means including a thermostat Ainiiuenced by the temperature of the outdoor air in control of said 1 damper means and operative to permit a maximum volume of outdoor air to be supplied to said space when the outdoor temperature is at a deerative to mrther reduce the supplying of outdoor air to theA space if the space temperature variesin the same direction from a predetermined value. f

' 15. A system of the class described, comprising,

in combination, circulating means for circulating outdoor air to a space the condition of which it is desired to control, air conditioning means for maintaining desired conditions within said space, damper means associated with the circulating means and operative to vary the volume of outdoor air supplied to said space, means including a thermostat iniiuenced by the temperature of the outdoor air in control of said damper means and operative to permit a maximum volume of outdoor air to be supplied to said space when the outdoor temperature is at a desired normal and to reduce'the volume of` outdoor air suppied to the lspace to a predetermined minimum if thev outdoor temperature varies to a predetermined value, and means including a device responsive to acondition indicative of the load on said air conditioning means for additionally controlling said damper means, said device being arranged to further reduce the supplying of outdoor air to the space when the load on said airconditioning LEO B. MILLER. HENRY F. DEVER. 

